Mechanical vibration isolation liquid helium re-condensation low-temperature refrigeration system

ABSTRACT

The present disclosure relates to a mechanical vibration-isolated, liquid helium recondensing cryogenic cooling system. The system according to some embodiments of the present disclosure includes: a closed-cycle cryogenic cooling system, a liquid helium recondensation cooling and vibration isolation system, and a temperature feedback control system. The present invention utilizes a closed-cycle cryogenic cooling system and may achieve low temperatures as low as 4.2 K and may consume substantially no helium gas or liquid helium. Using the cooling and vibration isolation system, liquid helium is generated and maintained through recondensation of helium gas. Not only does the technology effectively isolate the low-frequency vibrations produced by the closed-cycle cryogenic cooling system during operation, but it also resolves the issue of large fluctuations in the resulting temperature of the closed-cycle cryogenic cooling system. The disclosed technology can achieve a large-scale temperature regulation and is suitable for ultra-high vacuum environment based on high-temperature baking.

FIELD OF THE DISCLOSURE

The present disclosure relates to the technical field of cryogenic cooling. In particular, the present disclosure relates to a mechanical vibration-isolated, liquid helium recondensation cryogenic cooling device.

BACKGROUND

A cryogenic environment refers to an environment that is lower than −180° C. (93.15 K). The cryogenic technology has applications in physics, chemistry, material, biology, national defense, and information, etc. As science and technology advance, cutting-edge precision scientific research and technical applications not only need low-temperature environment (4.2 K), but also need a low-vibration and ultra-high vacuum environment. The vast majority of cryogenic cooling systems that meet the above criteria consume liquid helium, which is a scarce and expensive resource, increasing operating costs.

In order to avoid the dependence on liquid helium consumption of cryogenic cooling equipment, a mechanical vibration isolated, liquid helium consumption free, cryogenic cooling system (CN Application No. 201610002349.8, the disclosure of which is incorporated in its entirety by reference herein) was developed. This cryogenic cooling system utilizes a liquid helium consumption free, closed-cycle cryogenic cooling system for achieving the cooling effect, resolving the issue of cryogenic cooling systems consuming large amounts of liquid helium. This cryogenic cooling system utilizes helium heat exchange gas as a thermal medium, and also effectively isolates the mechanical vibration of the cryogenic cooling system. However, the working principles of the closed-cycle cryogenic cooling system can lead to cyclical changes in the cooling power. Furthermore, there are still restrictions of relatively low cooling power and relatively high temperature fluctuations for the cooling and vibration isolation technology using helium heat exchange gas cooling and vibration isolation interface. These reasons may cause that the cooling efficiency and temperature stability of the liquid helium consumption free, cryogenic cooling system to be lower than those of liquid helium consuming cryogenic cooling systems. Thus, it is desirable to develop a cryogenic cooling system that achieves a high temperature stability and mechanical vibration-isolated cryogenic cooling system and consumes substantially no liquid helium.

SUMMARY

At least one purpose of the present disclosure is to provide a cryogenic cooling system that isolates mechanical vibrations, has little temperature fluctuation, high cooling power, and also consumes substantially no helium gas or liquid helium. In other words, the system is a mechanical vibration-isolated, liquid helium recondensation cryogenic cooling system. The operation of this system may be compatible with low-vibration environments and ultra-high vacuum environments.

In some embodiments of the present disclosure, the mechanical vibration-isolated, liquid helium recondensation cryogenic cooling system includes: a closed-cycle cryogenic cooling system, a liquid helium recondensation cooling and vibration isolation system, and a temperature feedback control system. The closed-cycle cryogenic cooling system includes: a cold head, a compressor, and a helium pipeline connected between the compressor and the cold head. The liquid helium recondensation cooling and vibration isolation system includes: a cooling and vibration isolation interface, helium heat exchange gas, liquid helium generated by recondensation, and soft rubber used for sealing off the helium gas and isolating the vibration. The temperature feedback control system includes a temperature sensor, a heating element, and a feedback temperature control circuit.

In the liquid helium recondensation cooling and vibration isolation system, the cold head of the closed-circuit cryogenic cooling system extends into the cooling and vibration isolation interface. The helium heat exchange gas disposed between the cold head and the cooling and vibration isolation interface acts as a cooling medium. The soft rubber is connected to and seals the upper end of the cooling and vibration isolation interface and the cold head. The soft rubber seals off the helium heat exchange gas and isolates the low-frequency vibration of the cold head. Because the lowest temperatures of the cold head may be lower than 4.2 K, the helium gas heat exchange recondenses at the cooling and vibration isolation interface to form liquid helium. The liquid helium formed by recondensation possesses large latent heat, and can greatly increase the heat exchange capability between the cold head and the cooling and vibration isolation interface. Thus, the design of the mechanical vibration-isolated, liquid helium recondensation cryogenic cooling system can achieve larger cooling power and better temperature stability while also achieving a low-temperature, low-vibration environment.

In the temperature feedback control system, the heating element is disposed at the low-temperature end of the cooling and vibration isolation interface. The temperature sensor is disposed at the cooling and vibration isolating interface, and substantially covers a horizontal projection surface of the liquid helium formed through the recondensation. The temperature sensor is used to indirectly measure the liquid level of the liquid helium formed through recondensation, and the feedback temperature control circuit is used to control the output power of the heating element. The liquid helium level can be regulated through the temperature feedback control system in order to prevent vibrations introduced by a direct contact between the liquid helium surface and the cold head. The temperature feedback control system can also be used to achieve a wide range of temperature adjustment of the cooling system.

In some embodiments of the present disclosure, a thermal radiation shield may be disposed at the cooling and vibration isolation interface, to shield thermal leaks caused by the high-temperature radiation.

In some embodiments of the present disclosure, in order to allow the disclosed mechanical vibration-isolated, liquid helium recondensation cryogenic cooling system be compatible with the high-temperature baking conditions to achieve ultra-high vacuum environments, the liquid helium recondensation cooling and vibration isolation system can include materials such as stainless steel and oxygen-free copper as well as welding and sealing technology compatible with ultra-high vacuums.

In some embodiments of the present disclosure, the closed-cycle cryogenic cooling system can be, but are not limited to, Gifford-McMahon cryogenic cooling systems, Sterling cryogenic cooling systems, pulse tube cryogenic cooling systems, and improved cryogenic cooling systems based on principles of those systems. The cooling power and lowest achievable temperatures of the closed-cycle cryogenic cooling system may vary based on working principles and models.

The cooling system of the present disclosure may have the following advantages:

1. The liquid helium recondensation cooling and vibration isolation system utilized by the present disclosure consumes substantially no helium gas or liquid helium. This solution resolves the problem of cryogenic equipment consuming liquid helium, a scarce and expensive resource.

2. The disclose system uses recondensation technology to liquefy a portion of the helium heat exchange gas at the low-temperature end that generates liquid helium, greatly improving the system's cooling power and temperature stability. This solution resolves the problem of closed-cycle cryogenic cooling system experiencing temperature fluctuations at low temperatures.

3. The helium heat exchange gas cooling and vibration isolation interface of the present disclosure effectively isolates the low-frequency mechanical vibrations of the closed-cycle cooling system during operation, providing a cryogenic and low-vibration environment.

4. The temperature feedback control system of the present disclosure can achieve a liquid helium level control and can also achieve a large-scale temperature adjustment operation.

5. The system disclosed by the present disclosure can achieve low temperatures and low vibration under the conditions of consuming substantially no helium gas or liquid helium. The system can also operate in ultra-high vacuum environments, and can sustain the high-temperature baking to achieve an ultra-high vacuum environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates principles of a mechanical vibration isolated, liquid helium recondensation cryogenic cooling system device according to various embodiments of the present invention.

FIG. 2 illustrates a sectional diagram of a sample assembly of a cold head component and a liquid helium recondensation cooling and vibration isolation system of the cryogenic cooling system.

FIG. 3 schematically illustrates a sample assembly of a temperature feedback control system.

Numerals within the figures: 1—Closed-cycle cryogenic cooling system; 2—Liquid helium recondensation cooling and vibration isolation system; 3—User sample or device; 4—Temperature feedback control system; 5—Vacuum chamber; 6—Cold head; 7—Cooling and vibration isolation interface; 8—Helium heat exchange gas; 9—Liquid helium formed through liquidation or recondensation; 10—Experimental sample or experimental device; 11—Thermal shield; 12—Soft rubber; 13—Heating element; 14—First temperature sensor; 15—Second temperature sensor.

DETAILED DESCRIPTION

In order to further clarify the use of the present disclosure, embodiments have been presented below as well as reference diagrams for further detailed explanation of the present disclosure.

The disclosed cooling device may include: a closed-cycle cryogenic cooling system 1, a liquid helium recondensation cooling and vibration isolation system 2, and a temperature feedback control system 4. A user sample or user device 3 is disposed below the liquid helium recondensation cooling and vibration isolation system 2. Those components are enclosed in a vacuum chamber 5.

The closed-cycle cryogenic cooling system 1 includes: a closed-cycle cold head 6, a compressor, and a helium gas pipeline. The liquid helium recondensation cooling and vibration isolation system 2 includes: a cooling and vibration isolation interface 7, helium heat exchange gas 8, liquid helium formed through liquidation or recondensation 9, a thermal shield 11, and soft rubber 12. An experimental sample or experimental device 10 is disposed below the liquid helium recondensation cooling and vibration isolation system 2.

The temperature feedback control system 3 includes: the heating element 13, the first temperature sensor 14, and the second temperature sensor 15.

In the liquid helium recondensation cooling and vibration isolation system 2, the cold head 6 of the closed-cycle cryogenic cooling system 1 extends into the cooling and vibration isolation interface 7. The helium heat exchange gas 8 is disposed between the cold head 6 and the cooling and vibration isolation interface 7 acts as a cooling medium. The soft rubber 12 connects and seals the top end of the cooling and vibration isolation interface 7 and the cold head 6. While sealing the helium gas exchange gas, the soft rubber 12 also isolates the low-frequency mechanical vibration of the cold head 6. Caused by a cooling effect of the closed-cycle cold head 6, the helium heat exchange gas 8 is recondensed to form liquid helium at the cooling and vibration isolation interface 7, greatly improving the cooling power and temperature stability between the cold head 6 and the cooling and vibration isolation interface 7. The thermal radiation shield 11 is disposed at the cooling and vibration isolation interface 7 to shield against thermal leaks caused by high-temperature radiation.

The temperature feedback control system 3 includes the heating element 13, the first temperature sensor 14, the second temperature sensor 15, and the feedback temperature control circuit. The first temperature sensor 14 is disposed below a horizontal projection plane of a design liquid helium level. The second temperature sensor 15 is disposed above the horizontal projection plane of the design liquid helium level. By measuring the temperatures at the first and second temperature sensors 14, 15, and using the feedback control, the liquid helium level in the cooling and vibration isolation interface 7 can be regulated. When the cooling and vibration isolation interface 7 contains no liquid helium, both measurement temperatures of the first and second temperature sensors 14, 15 are above the phase transition temperature of helium gas (around 4.2 K). When the liquid helium level in the cooling and vibration isolation interface 7 is between the first and second temperature sensors 14, 15, the measurement temperature of the first temperature sensors 14 is equal to the phase transition temperature of helium gas, and the measurement temperature of the second temperature sensor 15 is higher than the phase transition temperature of helium gas. When the liquid helium level is higher than the second temperature sensor 15, both measurement temperatures of the first and second temperature sensors 14, 15 are equal to the phase transition temperature of helium gas. In addition, a large-scale temperature adjustment can also be achieved through the operation of the temperature feedback control system 3.

According to at least some embodiments of the present embodiment, a closed-cycle cooling system is used to resolve the issue of cryogenic cooling operation specifying large quantities of liquid helium. Using a helium heat exchange gas cooling and vibration isolation interface resolves the issue of cooler operation producing micron-level (and/or above micron-level) low-frequency vibrations. Using the liquid helium recondensation technology resolves the issue of large temperature fluctuations of closed-cycle systems under cryogenic temperatures. Using a temperature feedback control system to perform feedback temperature control can not only regulate the level of liquid helium formed by recondensation in the cooling and vibration isolation interface, but can also achieve large-scale temperature adjustment operations. Using materials such as oxygen-free copper and stainless steel for the cooling and isolation vibration interface in the vacuum environment is compatible with the high-temperature baking conditions specified by an ultra-high vacuum environment.

The specific embodiments above further describe the purposes, technical solutions, and beneficial outcomes of the present disclosure. It should be understood that the above descriptions are only specific embodiments of the present disclosure and are not limitations of the present disclosure. Any modification, equivalent replacement or improvement performed within the spirit or principle of the present disclosure should be included within the scope of protection of the present disclosure. 

1-3. (canceled)
 4. A cooling system, comprising: a closed-cycle cooling system including a closed-cycle cold head, a compressor, and a helium gas pipeline; a cooling and vibration isolation interface containing a helium heat exchange gas configured to conduct a heat exchange between the cold head and the cooling and vibration isolation interface; and a temperature feedback control system configured to detect a liquid helium level of a liquid helium stored in an low-temperature end of the cooling and vibration isolation interface.
 5. The cooling system of claim 4, wherein the temperature feedback control system includes at least one temperature sensor configured to detect the liquid helium level in the low-temperature end of the cooling and vibration isolation interface.
 6. The cooling system of claim 4, wherein the temperature feedback control system includes a first temperature sensor disposed below a horizontal projection plane of a design liquid helium level, and a second temperature sensor disposed above the horizontal projection plane of the design liquid helium level.
 7. The cooling system of claim 4, wherein the temperature feedback control system includes a first temperature sensor and a second temperature sensor, and temperature measurements of the first temperature sensor and the second temperature sensor are associated with the liquid helium level of the liquid helium stored in the low-temperature end of the cooling and vibration isolation interface.
 8. The cooling system of claim 4, wherein the temperature feedback control system includes a heating element disposed adjacent to the low end of the low-temperature end of the cooling and vibration isolation interface, and configured to heat the liquid helium stored in the low-temperature end of the cooling and vibration isolation interface.
 9. The cooling system of claim 4, wherein the liquid helium is generated through recondensation of the helium heat exchange gas of the cooling and vibration isolation interface.
 10. The cooling system of claim 4, wherein the helium heat exchange gas is configured to isolate a mechanical vibration of the cold head of the closed-cycle cooling system.
 11. The cooling system of claim 4, wherein the cold head of the closed-cycle cooling system extends into the cooling and vibration isolation interface.
 12. The cooling system of claim 4, wherein the closed-cycle cooling system further includes a compressor and a gas pipeline.
 13. The cooling system of claim 4, further comprising: a thermal heat shield disposed on the cooling and vibration isolation interface to shield radiation thermal leaks.
 14. The cooling system of claim 4, further comprising: a rubber sealing the cold head and a top end of the cooling and vibration isolation interface and configured to isolate a mechanical vibration of the cold head.
 15. A method of cryogenic cooling, comprising: conducting a heat exchange between a cold head of a closed-cycle cooling system and a cooling and vibration isolation interface by helium exchange gas; and recondensing a portion of the helium heat exchange gas into a liquid helium; and storing the liquid helium in a low-temperature end of cooling and vibration isolation interface.
 16. The method of claim 15, further comprising: collecting a first temperature measurement from a first temperature sensor disposed below a horizontal projection plane across the low-temperature end of cooling and vibration isolation interface; and collecting a second temperature measurement from a second temperature sensor disposed above the horizontal projection plane.
 17. The method of claim 16, further comprising: detecting a liquid helium level of the liquid helium stored in low-temperature end of cooling and vibration isolation interface; and regulating the liquid helium level through a heating element disposed adjacent to the low-temperature end of cooling and vibration isolation interface.
 18. The method of claim 17, wherein the detecting a liquid helium level comprises: in response to that the first temperature measurement and the second temperature measurement are above a phase transition temperature of helium gas, determining that the liquid helium level is above the second temperature sensor; and in response to that the first temperature measurement equals the phase transition temperature of helium gas and the second temperature measurement is above the phase transition temperature of helium gas, determining that the liquid helium level is between the first temperature sensor and the second temperature sensor.
 19. The method of claim 15, further comprising: shielding radiation thermal leaks by a thermal radiation shield disposed on the cooling and vibration isolation interface.
 20. The method of claim 15, further comprising: isolating a mechanical vibration of the cold head by the helium heat exchange gas.
 21. The method of claim 15, further comprising: isolating a mechanical vibration of the cold head by a rubber disposed to seal the cold head and a top end of the cooling and vibration isolation interface.
 22. The method of claim 15, further comprising: conducting a heat exchange between the low-temperature end of cooling and vibration isolation interface and an object to be cooled and disposed below the low-temperature end. 